J/A+A/659/A1 LOFAR Two-metre Sky Survey (LoTSS) DR2 (Shimwell+, 2022)
The LOFAR Two-metre Sky Survey (LoTSS). V. Second data release.
Shimwell T.W., Hardcastle M.J., Tasse C., Best P.N., Roettgering H.J.A.,
Williams W.L., Botteon A., A.Drabent, Mechev A., Shulevski A.,
van Weeren R.J., Bester L., Brueggen M., Brunetti G., Callingham J.R.,
Chyzy K.T., Conway J.E., Dijkema T.J., Duncan K., de Gasperin F., Hale C.L.,
Haverkorn M., Hugo B., Jackson N., Mevius M., Miley G.K., Morabito L.K.,
Morganti R., Offringa A., Oonk J.B.R., Rafferty D., Sabater J.,
Smith D.J.B., Schwarz D.J., Smirnov O., O'Sullivan S.P., Vedantham H.,
White G.J., Albert J.G., Alegre L., Asabere B., Bacon D.J., Bonafede A.,
Bonnassieux E., Brienza M., Bilicki M., Bonato M., Calistro Rivera G.,
Cassano R., Cochrane R., Croston J.H., V.Cuciti, Dallacasa D., Danezi A.,
Dettmar R.J., Di Gennaro G., Edler H.W., Ensslin T.A., Emig K.L.,
Franzen T.M.O., Garcia-Vergara C., Grange Y.G., Guerkan G., Hajduk M.,
Heald G., Heesen V., Hoang D.N., Hoeft M., Horellou C., Iacobelli M.,
Jamrozy M., Jelic V., Kondapally R., Kukreti P., Kunert-Bajraszewska M.,
Magliocchetti M., Mahatma V., Malek K., Mandal S., Massaro F.,
Meyer-Zhao Z., Mingo B., Mostert R.I.J., Nair D.G., Nakoneczny S.J.,
Nikiel-Wroczynski B., Orru E., Pajdosz-Smierciak U., Pasini T.,
Prandoni I., van Piggelen H.E., Rajpurohit K., Retana-Montenegro E.,
Riseley C.J., Rowlinson A., Saxena A., Schrijvers C., Sweijen F.,
Siewert T.M., Timmerman R., Vaccari M., Vink J., West J.L., Wolowska A.,
Zhang X., Zheng J.
<Astron. Astrophys. 659, A1 (2022)>
=2022A&A...659A...1S 2022A&A...659A...1S (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Radio continuum
Keywords: surveys - catalogs - radio continuum: general -
techniques: image processing
Abstract:
In this data release from the ongoing LOw-Frequency ARray (LOFAR)
Two-metre Sky Survey (LoTSS) we present 120-168MHz images covering
27% of the northern sky. Our coverage is split into two regions
centred at approximately 12h45m +44°30' and 1h00m +28°00' and
spanning 4178 and 1457 square degrees respectively. The images were
derived from 3,451 hrs (7.6 PB) of LOFAR High Band Antenna data which
were corrected for the direction-independent instrumental properties
as well as direction-dependent ionospheric distortions during
extensive, but fully automated, data processing. A catalogue of
4396228 radio sources is derived from our total intensity (Stokes I)
maps, where the majority of these have never been detected at radio
wavelengths before. At 6"resolution, our full bandwidth Stokes I
continuum maps with a central frequency of 144MHz have: a median rms
sensitivity of 83mJy/beam; a flux density scale accuracy of
approximately 10%; an astrometric accuracy of 0.2"; and we estimate
the point-source completeness to be 90% at a peak brightness of
0.8mJy/beam. By creating three 16MHz bandwidth images across the band
we are able to measure the in-band spectral index of many sources,
albeit with an error on the derived spectral index of >±0.2 which is
a consequence of our flux-density scale accuracy and small fractional
bandwidth. Our circular polarisation (Stokes V) 20" resolution
120-168 MHz continuum images have a median rms sensitivity of
95uJy/beam, and we estimate a Stokes I to Stokes V leakage of 0.056%.
Our linear polarisation (Stokes Q and Stokes U) image cubes consist of
480x97.6kHz wide planes and have a median rms sensitivity per plane
of 10.8mJy/beam at 4' and 2.2mJy/beam at 20"; we estimate the Stokes I
to Stokes Q/U leakage to be approximately 0.2%. Here we characterise
and publicly release our Stokes I, Q, U and V images in addition to
the calibrated uv-data to facilitate the thorough scientific
exploitation of this unique dataset.
Description:
The LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) Second
data release contains 120-168MHz images covering 27% of the northern
sky. The coverage is split into two regions centred at approximately
12h45m +44°30' and 1h00m +28°00' and spanning 4178 and 1457
square degrees respectively. A catalogue of 4396228 radio components
is derived from our 6" resolution total intensity (Stokes I) maps
where the median rms sensitivity is 83uJy/beam; the flux density scale
accuracy is approximately 10%; the astrometric accuracy is 0.2"; and
the estimated the point-source completeness is 90% at a peak
brightness of 0.8mJy/beam. Also included in the data release are:
three 16 MHz bandwidth images across the band, circular polarisation
(Stokes V) 20" resolution 120-168MHz continuum images; linear
polarisation (Stokes Q and Stokes U) image cubes at 4' and 20"
resolution both consisting of 480x97.6kHz wide planes; and the
calibrated uv-data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 204 4396228 Raw radio component catalogue of LoTSS-DR2
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See also:
J/A+A/622/A1 : LOFAR Two-metre Sky Survey DR1 source catalog (Shimwell+, 2019)
lofar-surveys.org : LOFAR surveys home page
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 22 A22 --- Source The radio name of the source, automatically
generated from RA and DEC (Source_Name)
24- 32 F9.5 deg RAdeg Right ascension (J2000) (RA) (1)
34- 39 F6.2 arcsec e_RAdeg rms uncertainty on RA (E_RA) (2)
41- 49 F9.5 deg DEdeg Declination (J2000) (DEC) (1)
51- 56 F6.2 arcsec e_DEdeg rms uncertainty on DE (E_DEC) (2)
58- 66 F9.3 mJy/beam Speak The peak Stokes I flux density per beam of
the source (Peak_flux)
68- 73 F6.3 mJy/beam e_Speak The 1-sigma error on the peak flux density
per beam of the source (EPeakflux)
75- 83 F9.3 mJy SpeakTot The total, integrated Stokes I flux density
of the source at the reference frequency
(Total_flux)
85- 91 F7.3 mJy e_SpeakTot The 1-sigma error on the total flux density
of the source (ETotalflux)
93- 98 F6.2 arcsec Maj FWHM of the major axis of the source,
INCLUDING convolution with the 6-arcsec
LOFAR beam (Maj)
100-105 F6.2 arcsec e_Maj The 1-sigma error on the FWHM of the major
axis of the source (E_Maj)
107-112 F6.2 arcsec Min FWHM of the minor axis of the source,
INCLUDING convolution with the 6-arcsec
LOFAR beam (Min)
114-119 F6.2 arcsec e_Min The 1-sigma error on the FWHM of the minor
axis of the source (E_Min)
121-126 F6.2 arcsec DCMaj The FWHM of the major axis of the source,
after de-convolution with the 6-arcsec
LOFAR beam (DC_Maj)
128-133 F6.2 arcsec e_DCMaj The 1-sigma error on the FWHM of the
deconvolved major axis of the source
(EDCMaj)
135-140 F6.2 arcsec DCMin The FWHM of the minor axis of the source,
after de-convolution with the 6-arcsec
LOFAR beam (DC_Min)
142-147 F6.2 arcsec e_DCMin The 1-sigma error on the FWHM of the
deconvolved minor axis of the source
(EDCMin)
149-154 F6.2 deg PA The position angle of the major axis of the
source measured east of north, after
de-convolution with the 6-arcsec LOFAR
beam (PA)
156-161 F6.2 deg e_PA The 1-sigma error on the position angle of
the deconvolved major axis of the source
(E_PA)
163-168 F6.2 deg DCPA The position angle of the major axis of the
source measured east of north, after
de-convolution with the 6-arcsec LOFAR
beam (DC_PA)
170-175 F6.2 deg e_DCPA The 1-sigma error on the position angle of
the deconvolved major axis of the source
(EDCPA)
177-182 F6.3 mJy/beam Islrms The average background rms value of the
island (Isl_rms)
184 A1 --- SCode A code that defines the source structure in
terms of the fitted Gaussian components
(S_Code) (3)
186-196 A11 --- Mosaic The name mosaic in which the FITS image can
be found (Mosaic_ID)
198 I1 --- Npoint The number of pointings that are mosaiced at
the position of the source
(Number_Pointings)
200-204 F5.3 --- MaskFract The fraction of the source that is in the
CLEAN mask (Masked_Fraction)
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Note (1): Positions from PyBDSF or combination of PyBDSF components.
Note (2): Posiiton errors estimated by PyBDSF. Only fitting uncertainties are
included.
Note (3): Code as follows:
S = indicates an isolated source that is fit with a single Gaussian
C = represents sources that are fit by a single Gaussian but are within an
island of emission that also contains other sources
M = is used for sources with are extended and fit with multiple Gaussians
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Acknowledgements:
Timothy Shimwell, shimwell(at)astron.nl
(End) Patricia Vannier [CDS] 07-Feb-2022